Circular antenna array system scanning switch



F. STEINER 3,

CIRCULAR ANTENNA ARRAY SYSTEM SCANNING SWITCH Aug. 7, 1962 4 Sheets-Sheet 1 Filed Feb. 18, 1959 W6. 3% QQQQQ Mm Wild INVENTOR.

F STEIN'ER F. STEINER 3,048,843

CIRCULAR ANTENNA ARRAY SYSTEM SCANNING SWITCH Aug. 7, 1962 4 Sheets-Sheet 2 Filed Feb' 18, 1959 INVENTOR.

F STEINER Aug. 7, 1962 F. STEINER 3,048,843

CIRCULAR ANTENNA ARRAY SYSTEM SCANNING SWITCH Filed Feb. 18, 1959 4 Sheets-Sheet 3 tms Fig.6

INVENTOR.

F STEINER CIRCULAR ANTENNA ARRAY SYSTEM SCANNING SWITCH Filed Feb. 18, 1959 F. STEINER Aug. 7, 1962 4 Sheets-Sheet 4 INVENTOR. STE INER United States Patent fifice 3,948,843 Patented Aug. 7, 1962 3,048,843 CIRCULAR ANTENNA ARRAY SYSTEM SCANNHNG SWITCH Fritz Steiner, Pforzheim, Germany, assignor to International Standard Electric Corporation, New York, N.Y.,

a corporation of Delaware Filed Feb. 18, 1959, Ser. No. 794,014 Claims priority, application Germany Feb. 22, 1958 11 Claims. (Cl. 343-113) The present invention relates to a switching device for the cyclically sequential connection of fixed antenna elements of a circular antenna array to a receiving device for the purpose of determining the direction of incidence of electromagnetic waves.

Various methods are known for directional receiving systems, in which a circular antenna array is cyclically scanned by electrical switching means. From the phase modulation of the incoming wave a bearing signal is derived by means of a phase comparison with a reference signal effecting the scanning.

Furthermore a direction-finding method has been proposed in which a circular antenna array is scanned and where the incoming wave is frequency modulated. The scanning itself is effected in such a way that to a continuously rotating simulated motion of a single antenna element there is superimposed a motion rapidly moving to and fro in a predetermined sector. By means of this simulated rapid motion to and fro the frequency deviation produced on the one hand is great enough to be evaluated, and on the other hand the bearing errors which are due to the group delay of the receiver, and which correspond to a slow continuous simulated antenna motion are small.

A direction finder operating on this principle is preferably designed in the conventional manner as a wide aperture direction finder to keep the bearing errors to a minimum. Technically this proposed directionfinding method has formerly been carried out in such a way that individual antennas are connected sequentially to the receiver by means of switching diodes. In the switching of these diodes there are used two trains of pulses, of which one train simulates a rapid forward and backward motion, while the other one simulates a slow and continuously progressive motion of an antenna element. The connection of the antenna element which is carried out in this case electronically, is performed by means of pulse generators of a different repetition rate in combination with delay lines and voltage-dependent resistors, such as the aforementioned diodes arranged in the antenna leadins. In this case, however, the investment in switching equipment is a considerable one.

A direction finder of the Doppler type has been known in which a circular antenna array is scanned by means of a capacitively coupled switch and in which the fre quency deviation resulting therefrom is utilized for determining the direction. (This system has been described in an article by Fantoni and Benoit, which was published in the IRE Convention Record, part 8, March 19-22, 1956.) This system, however, bears the disadvantage which is already well known in direction finding systems of the Doppler type, where slow scanning of the antenna system is used, namely, the frequency deviation or lowfrequency bearing voltage obtained therefrom is very small and, therefore, incapable of being utilized for the direction determination purpose. Furthermore if a rapid scanning of the antenna is used the group delay produced by the receiver is within the range of the frequency variation and therefore causes considerable bearing errors.

According to this invention it is now proposed to carry out a scanning of a circular antenna array by means of a correspondingly designed rotating commutator which can be operated either galvanically (with the aid of collector brushes), capacitively, photoelectrically or inductively in such a way that a slow continuous effective antenna rotation is combined with a rapid motion to and fro in a small sector. Expressed in mathematical terms the apparent antenna motion is characterized by the superposition of a linear function with any other suitable periodical function.

The scanning switch according to this invent-ion is for a circular antenna array which simulates the motion of an antenna element. In particular this scanning switch is utilized from the simulation of pilgrim-step motions with the aid of a stator and a rotor in which the order of succession of the scanning operations of N input lines with the numerals n in successive scanning steps and with the numerals in corresponding to an assignment. Mathematically this relation is expressed by rr==f (m) and is formulated arbitrarily with respect to the first p scanning steps, and in which the further order of succession of the scanning operations with the oscillation period p progresses in such a way that the numeral or number of input lines which is scanned during the scanning step m+p is greater by unity than the number of the lines scanned during the scanning step In. This is characterized in that on the stator there are arranged N switch segments at an equally spaced relation d, and on the rotor p there are arranged further switch segments at the space relation m 1 a =d f(m)1-T with m -2,3 p where (2 is equal to the spacing between adjacent rotor segments.

The following invention will now be described in particular with reference to FIGS. 1-7 of the accompanying drawings, in which:

FIG. 1 shows a Doppler-type direction finder system employing a capacitive scanning switch according to the invention for simulating a simple pilgrim-step motion.

FIG. 2 shows another embodiment of the scanning switch according to the idea of the invent-ion, which operates on an inductive coupling principle,

FIG. 3a schematically shows part of the stator arrangement,

FIG. 3b schematically shows a rotor and stator arrangement for effecting a forward pilgrim-step motion of the antenna,

FIG. 3c schematically shows a rotor and stator arrangement for effecting a backward pilgrim-step motion of the antenna,

FIG. 4 shows the electrical equivalent circuit diagram of the scanning switch extending from the connecting point of the antennas to the receiver inlet,

FIG. 5 shows one kind of the apparent antenna motion (sinusoidal) as plotted on a time base (milliseconds).

FIG. 6 shows the amplitude modulation resulting on account of the scanning of the antenna array according to FIG. 5 at the output of the receiver 17 in FIG. 1, and

FIG. 7 shows a general shape of the antenna motion in a graphical representation.

The direction finder as shown in principle in FIG. 1 of the accompanying drawings is equipped with a capacitive scanning switch which according to the invention allows a very simple pilgrim-step scanning motion which for purposes of explanation is in this particular instance three steps in the forward direction and two steps in the backward direction. The example of this simple type of pilgrim-step scanning motion is illustrated graphically in FIG. 7. But it should he understood that any sequential pilgrim-step scanning motion can be used consisting of a fixed number of integral steps in one direction followed by a fixed number of steps in the opposite direction other than the number of steps used in the first direction. Furthermore, referring to FIG. 1, the capacitive switch segments of the stator 2 and rotor 7 may also be adapted to a photoelectric arrangement where the corresponding segments would then be holes through which a light ray may pass for controlling a photelectric cell.

One part of the direction finder in FIG. 1 is the circular antenna-array system 1 comprising e.g. l2 antenna elements, each of which is connected via cable with one segment 3 of the stator 2. On the stator 22 there are also provided just as many aligned collector segments 4, all of which are conduetively connected with each other at the point P. To the point P there is also connected a cable 5 leading to the input of a receiver 17. The rotor a driven by motor 14- is mounted a slight distance from the stator 2 and comprises the segments 7 consisting of two parts illustrated in FIG. 1 and which are connected with each other by means of small inductances. In the described example, the stator segments, as well as the collector and rotor segments, are all of the same width. The function of the inductances 22 will be described hereinafter. Hence, if the stator and collector segments 3, 4 are bridged by one rotor segment 7, there will exist a capacitive coupling between the respective antenna which is coupled to the stator segment 3 and to the input of the receiver 17. On account of the successive, periodical coupling of the antenna elements there is produced at the collecting point P or at the input of the receiver 17, a frequency-modulated high-frequency voltage. Thereupon, at the output of this frequency dcmodulating receiver 17, there exists a low-frequency voltage as indicated in the curve of FIG. 6. On the axis of rotation to of the motor 14 there is also provided a phonic wheel 8 of the conventional type comprising a number of teeth corresponding to the number of antennas. An alternating-current voltage will be produced in winding 9 corresponding to the rapid scanning of the antenna array. This AC. voltage is used as the phase-locked reference signal. For the purpose of effecting an adjustment with respect to the toothed-wheel rim, the winding 9 of the phonic wheel 8 is angularly displaceable by a small amount, so that the phase of this reference signal is adjustable by a desired amount. By means of this arrangement it is rendered possible to compensate for the group delay of the receiver 17, which occurs as a result of the slow scanning frequency. The voltage produced by means of the phonic wheel 8 is fed via slip-rings or collector rings 31 to the rotor winding 13 of a ring-type goniorneter. The stator Winding 12 of the goniometer is closed in itself and has four tappings which are staggered by 90 From two opposing tappings there are respectively taken off two voltages of the shape as shown in FIG. 6. The envelopes of these voltages are phase-shifted with respect to each other by 90. The envelope of the output voltage of the receiver 17 likewise has the shape, as indicated in FIG. 6. But this voltage is phase-shifted with respect to the other envelopes by the corresponding direction of incidence of the received electromagnetic waves. Each of the two reference signals which are phase-shifted by 96 is now fed in the conventional manner via conductor leads l5 and 16 together with the signal containing the bearing information from receiver 17, via line 18 to a network enabling a product formation and comprising a conventional type of phase comparator indicator 19. As is well-known, the DC. component of each of these products is then in proportion to the sine or the cosine respectively of the angle of incidence of the wave front.

In order to explain the idea of this invention, and for providing a numerical reference value it is assumed that the illustrated pilgrim-step motion, which produces a slow, continuous scanning is efiected with a frequency of 50 c.p.s., which corresponds to the number of rotations of the rotor 7. To this slow motion which progresses continuously in one direction there is combined a rapidly oscillating motion with a frequency of 1:700 cycles in a sector of about :45 degrees. This kind of simulated antenna motion on the whole is graphically shown in FIG. 5 which illustrates one complete rotation of 360 over the time base t (milliseconds). The amplitude modulation resulting therefrom is plotted in PEG. 6 over the same time base. In this example, the envelope corresponds to the slow, continuous scanning motion and the voltage which is modulated in a carrierless manner with this voltage corresponds to the rapid, oscillating motion. As has been previously stated, the envelope is used for the direction-determination purpose.

The scanning effected in accordance with the showing of FIG. 5 (3 steps in the forward direction and 2 steps in the backward direction) of the individual antennas is accomplished with the aid of a capacitive switch consisting of stator 2 and a rotor 7, whose schematic representation with respect to the stator is given in FIGS. 3a c. The drawing of FIGS. 3a to 312 may also be understood to be e.g. a cylindrical arrangement developed on a plane, in which case the stator and collector segments 3, 4 are arranged on an outer cylinder, and the rotor segments 7 (see FIG. 1) may be arranged on an internal second cylinder.

The stator of the scanning switch is provided with stator segments 3 corresponding to the number of antennas to be commutated. Each of these stator segments 3 is connected with its associated antenna by means of a concentric cable. Assigned to these stator segments, but insulated therefrom are the collector segments 4 which are equal in number and which are provided on the same carrier component. Collector segments 4 are interconnected at point P and lead to the input of receiver 17. At a small distance opposite this stationary stator component 2 there is arranged a rotating component comprising a small number of segments 7, of which each consists of two parts as is shown in FIG. 1. One part bridges or overlaps the stator segment 3, while the other part overlaps the corresponding collector segment 4. The spaces between the stator and the collector segments are filled with metal coatings, as is indicated by the shaded portions in FIG. 3a. For the purpose of achieving a better electrical separation of the individual segments, as well as for the purpose of providing the necessary shielding, these metal coatings are connected to a ground conductor. These ground conductors accompanying both the stator and collector segments (and which are indicated by the shaded portions in FIG. 3a) are arranged at such a distance from the respective segments that they have the same characteristic impedance, as that of the coaxial cable leading to the antenna, namely, 60 ohms. In particular the continuously extending ground conductors also allow the energy received by the antenna to be only transferred to the collector segments 4, whenever a rotor segment bridges or overlaps both a stator segment 3 and a collector segment 4. Furthermore, the rotor segments 7 are capacitively grounded when not positioned opposite to a stator and collector segment. On account of the fact that the characteristic impedance of the scanning switch is approximately equal to that of the cable leading to the antenna, the currents can be transferred in a continuous line from the antenna via the stator segment 3, the rotor segment 7 and the collector segment 4 to the input of the receiver 17.

In accordance with a further embodiment of this invention the aforementioned two parts of each rotor seg- -ment 7 are respectively connected with each other by means of a small inductance 22 constituting, together with the transmission capacitance of the two movable parts of the rotor-segments with respect to the stationary segments, at series-resonant circuit having its resonant frequency near the middle of the frequency range to be transmitted.

Furthermore, the collector segments 4 connected to each other and leading to the receiver 17 are connected to ground by a small inductance 24 which, together with the switch capacitances (segments 4, FIG. 3a, to ground) form a parallel-resonant circuit having its resonant frequency near the middle of the frequency range to be transmitted. On account of the two resonant circuits it is now possible to achieve a wideband impedance matching in a conventional manner, and the attenuation from the point P to the input of the receiver 17 may be kept negligibly small within a predetermined frequency range.

The equivalent diagram of the circuit arrangement is shown in FIG. 4. In this arrangement the capacitor 21 corresponds to the capacitance of stator segment 3 (FIG. 3a) with respect to rotor segment 7, see FIG. 1, part A (FIG. 31)), while the capacitor 23 corresponds to the capacitance of collector segment 4 (FIG. 3a) with respect to segment 7, see FIG. 1, part B (FIG. 31)). These two series-arranged capacitors, together with inductance 22, form the above-mentioned series-resonant circuit, whereas the capacitor 25, which is formed by the switch capacitance of the collector segments 4 (FIG. 3a) to ground together with inductance 24 represent the parallel-resonant circuit.

Referring now specifically to FIGS. 3a to 30, the arrangement of the segments on stator 3 and rotor 4 will be better understood with respect to the pilgrim-step scanning motion of this invention. The distance d shown on FIG. 3a corresponds to the mutual spacing between the central line of adjacent stator segments.

As was previously stated diiferent combinations of pilgrim-step antenna scanning may be used. For instance, there may be chosen a motion consisting of four steps in the forward direction and three steps in the back- Ward direction or even 3 steps in the forward direction and 2 steps in the backward direction. The number of rotor segments and the spaced relation resulting from the given general formula which is hereinafter stated is represented graphically in a more general manner in FIG. 7. The spaced relation of the stator segments is assumed to be d as shown in FIG. 3a. The number of individual scanning steps at have a period p and the order of succession of the scanning operation of the input lines (antennas) with the numerals n is assumed to be given by the function n=f(m), as is represented by way of example in the curve of FIG. 7. The scanning of the individual antenna elements is now supposed to proceed in such a way that upon completion of one period p there is coupled the next antenna element so that the number of input lines or antennas, scanned during the scanning step m-l-p, is by unity greater than the number of the lines scanned during the scanning step m. It should be understood that this condition applies to each arbitrary point of the curve or to each arbitrary number n of the input lines respectively. In order to indicate this there are inserted at arbitrary points, shaded triangles, and it will be seen that the value of the function n:f(m) in the next successive period is always greater by unity than the one in the preceding period. In other words, upon completion of one period p there is always coupled the next successive input line of the circuit antenna array.

Under these conditions there results a number of p rotor segments and the mutual spacing between the central lines of adjacent rotor segments is given by the formula a =d[f(m) 1- wherein m=2, 3 p is to be inserted.

The width of the individual rotor segment 7 likewise results from this formula, in that in the most simple case it is equal to that of the stator segments. Thus, whenever there is a scanning-step m there is also supposed to correspond a different value m=f(m). However if the same input line with the same number as before is connected upon the stepping of one scanning step it can be seen that the distance or spacing a of the rotor 6 segment 7 will become zero, in other words, its width will be double its size.

In the assumed and most simple example with the three scanning steps in the forward direction and two scanning steps in the backward direction the stator segments have a width of /5 (one-fifth) of the spacing (d), and a mutual spacing of /5 between adjacent segments. The rotor segments as illustrated in FIG. 3b likewise has a width of /5 and, in accordance with the formula of proportion has a spacing between adjacent rotor segments of In order to clearly illustrate the forward pilgrimstep scanning motion of this invention, let us refer specifically to the schematic representation of FIG. 3b where the rotor segments are aligned in such a manner that rotor segment A is positioned one step to the left of the first stator segment M. As the rotor is advanced clockwise or from left to right in the direction of the arrow the rotor segment A in its first step will be directly beneath stator segment M. As the rotor is advanced stepby-step the rotor segments A, B and C will be positioned in succession directly beneath a succession of stator segments MNO etc. The following table will illustrate which of the stator and rotor segments will be capacitively coupled as the rotor 7 progresses clockwise in a step by-step motion.

Table I Step positions: Coupled stator segments 0 1 a- M 2 N 3 O 5 6 N 7 O 8 P 10 11 O 12 P 13 Q As can be noted from the above table, stator segment M is coincident with rotor segment A in the first step and stator segment N Will be coincident with rotor segment B in the second step. Thus as viewed from FIG. 1 the rotor 6 is continuously moving in a clockwise direction. The segments of the rotor are so spaced that the resultant effect of the scanning motion is to connect each antenna element to the receiver in a pilgrim-step order. For example, in the system as described above which has 12 antenna elements, the motion of the capacitive scanning switch is such that initially antenna elements 1, 2 and 3 are successively scanned, and then followed by a second scan of antenna elements 2, 3 and 4-, which is further followed by a third scan of antenna elements 3, 4 and 5 etc., until the entire antenna array has been scanned. Thus, this type of pilgrim-step scanning motion produces a slow continuous scanning which corresponds to the number of rotations or the frequency of the rotor 7 which was previously stated to be 50 c.p.s., having superimposed thereon a rapid oscillating motion of a frequency of about 1500 c.p.s. in a sector of about i45.

Now let us refer to FIG. 3c which illustrates the backward pilgrim-step scanning motion. Here the mutual spacing between adjacent rotor segments 7 is 7 of the mutual spacing of the stator and the width of each rotor segment is /5. The rotor segments are shown initially aligned in such a manner that rotor segment A is positioned two steps to the left of the first stator segment M, and as can be seen from this figure rotor segment C is coincident with a stator segment. As the rotor is again advanced one step in the clockwise direction or in the guesses direction of the arrow, rotor segment B will now be coincident with stator segment N, and as the rotor is advanced an additional step rotor segment A will be coincident with stator segment M. The following table will illustrate which of the stator and rotor segments will be capacitively coupled as rotor 7 progresses clockwise successively, in a step-by-step motion.

Thus with the particular spacing of 93 between adjacent rotor segments as illustrated in this figure a backward pilgrim-step scanning motion can be achieved.

Since the capacitive switchover from one antenna to the next one is not effected suddenly, but rather continuously or gradually, which is mainly due to the fact that the capacitance of the stator, collector and rotor segments with respect to each other gradually assume the maximum value, there is achieved a better simulation of an antenna motion than would be possible by means of a spasmodic switchover which occurs when switching or gating diodes are used instead of the capacitive switching as illustrated in the above invention.

In the described particular example of a pilgrim-step motion with three steps in the forward direction and two steps in the backward direction there has been described a linear motion in either direction. However, by means of a sufficiently greater number of antenna elements, as well as by a fine subdivision of the switching elements or scanning steps and by a corresponding selection of the width and the distances of the rotor segments in accordance with the general idea of the invention, it is possible to approximate a sinusoidal scanning.

In FIG. 2 there is shown another embodiment relating to the scanning switch according to the idea of the invention, which is based on the inductive coupling principle.

The individual antennas are applied by means of capacitors 28 28 to coupling coils 26 26 the other winding ends of which are connected to ground. Between the individual coils there are provided shielding walls 31, and each coupling circuit consisting of the capacitor 28 and the inductance 26 is balanced to seriesresonance for the medium frequency range to be transmitted. On the same base there are mounted additional coupling coils 27 -27 which are connected in parallel and are tuned by means of capacitor 29 for impedance matching at the medium operating frequency range. One end of the coupling coil is applied to the ground while the other end is connected to the point P and to the receiver 17 (FIG. 1). A strong or intensive coupling of the coils 26 and 27 and, consequently, a transfer of the antenna energy to the receiver is accomplished with the aid of ferro-magnetic elements 30 3i which are mounted to a rotor in accordance with the points of view 8 relating to the proportion and arrangement given in the exampie relating to the capacitive scanning switch described hereinbefore.

Analogously, the whole arrangement is also suitable for use with transmitters, when the reference signal is transmitted as well, eg via an auxiliary carrier or in an amplitude-modulated fashion.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. A scanning switch comprising a stator having an outer portion and an inner portion, a first group of segments radially positioned about said outer portion and spaced from each other, a second group of segments corresponding in number to the segments of said first group and aligned therewith, one of said group of segments having their segments interconnected, said second group of segments radially positioned about said inner portion and spaced from said first group of segments and from each other, a plurality of input lines equal in number to the number of segments in a group, means to connect said input lines with the corresponding segment of one of said groups, an output line, means to connect an output line with all of the segments of the other group, a rotor having a radially positioned rotor segment adapted to be aligned progressively with said segments of said first and second groups as the rotor is rotated and positioned in a coupling relation thereto, said rotor segment bridging the space between said segments of said first and second groups to provide coupling therebetween, and means for rotating said rotor to provide successive and retrogressive coupling of said input lines to said output line.

2. A scanning switch as defined in claim 1 further comprising means connected to the rotor for producing a variable reference voltage, and means for comparing said reference voltage with the signal produced on said output line for producing an indication.

3. in a direction finding system having a scanning switch as defined in claim 1 comprising an antenna array raving elements circularly spaced a predetermined distance from each other corresponding to the number of segments in a group, and means for connecting said plurality of input lines to said antenna elements.

4. A scanning switch as defined in claim 1, wherein the coupling between said rotor segment and said segments of said first and second group is capactive.

5. A scanning switch as defined in claim 1 further comprising means for providing a plurality of input line scans for each rotation of the rotor, the cycles of each scan having a fixed number of steps, said rotor comprising a plurality of segments said rotor segments having a different mutual spacing than the mutual spacing of the stator segments, the mutual spacing of the rotor segments differing from that of the mutual spacing of the stator segments by an amount equal to the distance traversed by said rotor segment in one step.

6. A scanning switch as defined in claim 5, wherein the number of rotor segments is equal to the number of input lines scanned in a cycle.

7. A scanning switch comprising a stator having an outer portion and an inner portion, a first group of segments radially positioned about said outer portion and spaced from each other, a second group of segments corresponding in number to the segments of said first group and aligned therewith, one of said group of segments having their segments interconnected, said second group of segments radially positioned about said inner portion and spaced from said first group of segments and from each other, a plurality of input lines equal in number to the number of segments in a group, means to connect said input lines with the corresponding segment of one of said groups, an output line, means to connect an input line with all of the segments of the other group, a shielding metallic member positioned between a pair of aligned segments of the first and second groups and the next adjacent pair of segments, said member being connected to ground and spaced a predetermined distance from said pairs of segments so that the characteristic impedance from the segments to the shielding member is approximately equal to the impedance of the input lines, an inductance connected between output line and the segments connected thereto to form a parallel resonant circuit, a rotor having a radially positioned rotor segment adapted to be aligned progressively with said segments of said first and second groups as the rotor is rotated and positioned in a coupling relation thereto, said rotor segment brid ing the space between said segments of said first and second groups to provide coupling therebetween, and means for rotating said rotor to provide successive coupling of said input lines to said output line.

8. A scanning switch comprising a stator having an outer portion and an inner portion, a first group of segments radially positioned about said outer portion and spaced from each other, a second group of segments corresponding in number to the segments of said first group and aligned therewith, one of said group of segments having their segments interconnected, said second group of segments radially positioned about said inner portion and spaced from said first group of segments and from each other, a plurality of input lines equal in number to the number of segments in a group, means to connect said input lines with the corresponding segment of one of said groups, an output line, means to connect an output line with all of the segments of the other group, a rotor having a radially positioned rotor segment adapted to be aligned progressively with said segments of said first and second groups as the rotor is rotated and positioned in a coupling relation thereto, said rotor segment bridging the space between said segments of said first and second groups to provide coupling therebetween, said rotor seg ment further comprising two conductive parts Which are connected by means of an inductance, said conductive parts forming a series resonant circuit with said inductance, and means for rotating said rotor to provide successive coupling of said input lines to said output line.

9. A scanning switch comprising a stator having an outer portion and an inner portion, a first group of segments radially positioned about said outer portion and spaced from each other, a second group of segments corresponding in number to the segments of said first group and aligned therewith, one of said group of segments having their segments interconnected, said second group of segments radially positioned about said inner portion and spaced from said first group of segments and trom each other, a plurality of input lines equal in number to the number of segments in a group, means to connect said input lines with the corresponding segment of one of said groups, an output line, means to connect an output line with all of the segments of the other group, a rotor having a radially positioned rotor segment adapted to be aligned progressively with said segments of said first and second groups as the rotor is rotated and positioned in a coupling relation thereto, said rotor segment bridging the space between said segments of said first and second groups to provide coupling therebet'ween, the coupling between said rotor segment and said segments of said first and second group being inductive, and means for rotating said rotor to provide successive coupling of said input lines to said output line.

10. A scanning switch for a circular antenna array having a plurality of antennas for simulating antenna element motion, comprising a stator and a rotor, said stator having a first group of segments equal in number to said plurality of antennas and spaced equidistant about a common point, a second group of segments corresponding in number to the segments or" said first group and disposed in spaced alignment therewith, means coupling together the segments of said second group, means coupling each of said antenna elements to a segment of said first group, said rotor comprising a plurality of segments disposed thereon and adapted for alignment with said aligned segments of said first and second groups in bridging relationship thereto, means for rotating said rotor relative to said stator to provide successive and retrogressive coupling of said segments of said first and second groups whereby signals received at said antenna array are coupled from the segments of said first group to the segments of said second group in said successive and retrogressive manner.

11. A scanning switch according to claim 10 wherein the switch segments of said first group carried by said stator are spaced apart a distance d and the switch segments disposed on said rotor are spaced apart a distance a =d[f(m) -1 where ](m) equals the number of antennas, m equals the number of individual scanning steps and p equals the period of scan of in steps.

References Cited in the file of this patent UNITED STATES PATENTS 2,457,127 Chesus et a1 Dec. 28, 1948 2,769,159 Moore Oct. 30, 1956 2,902,673 Hare Sept. 1, 1959 2,953,782 Byatt Sept. 20, 1960 2,961,655 Magnuson Nov. 22, 1960 

